1. Technical Field
The present invention relates to an optical writing control device, an image forming apparatus, and a method of controlling an optical writing device.
2. Description of the Related Art
In recent years, there has been a trend to promote the digitization of information. Image processing apparatuses such as printers and facsimiles that are used to output digitized information and scanners used to digitize documents have become indispensable.
In many cases, such an image processing apparatus is configured as a multifunction peripheral that can be used as a printer, a facsimile, a scanner, and a copying machine by including an image capture function, an image forming function, a communication function, and the like.
Among such image processing apparatuses, an electro-photographic image forming apparatus is widely used to output digitized documents. The electro-photographic image forming apparatus exposes a photosensitive element to form an electrostatic latent image. Then, the apparatus develops the electrostatic latent image with developer such as toner to form a toner image. Finally, the apparatus transfers the toner image onto a piece of paper to output the paper.
For an electro-photographic image forming apparatus, a linear light source such as an LEDA (Light Emitting Diode Array) may be used. The LEDA includes a plurality of LEDs (Light Emitting Diodes), which are arranged in a line along a main scanning direction as a light source to expose the photosensitive element. In such a linear light source, the diodes are classified into certain number of groups, and each group is subject to emission control, such as time-division emission control.
By applying such time-division control, the apparatus can reduce electric power required to illuminate the diodes, compared to simultaneous control, which illuminates all diodes simultaneously. On the other hand, an exposure position for each diode varies along with rotation of the photosensitive element, since the plurality of diodes are arranged in parallel to the rotation axis of the photosensitive element.
In a conventional technology, it is known to reduce an illuminating period for suppressing the exposure position variation. Moreover, it is also known that a part of the LEDA can be turned off to reduce power consumption during neutralization of the photosensitive element. However, typical exposure process of the photosensitive element needs severe timing control. For example, the conventional neutralization processes turn on all LED elements simultaneously, such that electric current exceeds a predetermined limit of power consumption. Therefore, an improved control is needed.
Because a typical full-color image forming apparatus has a plurality of image forming units, it is necessary to consider the total power consumption by the plurality of image forming units—not just that of one image forming unit. Moreover, more accurate control of the timing of illumination in the image forming process is needed in order to improve the neutralization process of the photosensitive element.